1. Field of Endeavor
Example embodiments provide compositions suitable for forming organic insulating films, methods for forming organic insulating films using such compositions, and organic thin film transistors comprising an organic insulating film formed by one of the methods. More specifically, example embodiments provide compositions for forming an organic insulating film which comprise an ultraviolet (UV) curing agent, a water-soluble polymer and a water-soluble fluorine compound; methods for forming organic insulating films using the composition in which an organic insulating film can be patterned without the need for an etching process using a photoresist. The use of compositions and methods as disclosed herein are capable of producing insulating films and corresponding structures whereby properties, for example, the hysteresis, of the organic insulating film can be improved. The use of compositions and methods as disclosed herein are capable of producing organic thin film transistors that incorporate one or more insulating films manufactured according to one or more methods as disclosed herein and which may exhibit improved yield, performance and/or reliability attributable to the inclusion of the improved organic insulating film.
2. Description of the Related Art
In recent years, a variety of polymeric materials have been investigated for their potential as electrical and electronic materials suitable for a wide variety of applications, e.g., functional electronic and optical devices as insulator and/or semiconductor materials. Polymeric materials may provide one or more advantages over previous materials including, for example, the relative ease with which they can be molded into fibers and films, improved flexibility, increased conductivity and reduced production costs. Research relating to electrically conductive polymers and their use in fabricating semiconductor active regions for organic thin film transistors has been ongoing for at least about 25 years.
Organic thin film transistors can be fabricated using relatively simple processes, such as printing, at relatively low cost. In addition, advantages associated with organic thin film transistors include relatively simple processes and their generally good compatibility with flexible substrates. In light of these advantages, a number of studies on organic thin film transistors are now ongoing around the world. Indeed, it is anticipated that organic thin film transistors will be particularly useful in fabricating driving devices for active displays and in fabricating plastic chips that may, in turn, be incorporated into smart cards and/or inventory tags, for example RFID products.
The formation of organic insulating films in the fabrication of organic electronic devices, for example, display devices (e.g., electroluminescence (EL) devices and light-emitting diodes (LEDs)) is one of the most promising applications of these technologies. Although various methods using, for example, polyimides, benzocyclobutene (BCB), photoacryl, and other suitable materials for fabricating organic insulating films have been disclosed, the performance of such organic insulating materials have been generally considered less satisfactory than conventional inorganic insulating materials and have not, therefore, been widely adopted as replacements for inorganic insulating films in semiconductor device fabrication.
Several attempts have been made to address the noted deficiencies of the organic insulating materials shortcomings. One approach suggests that the performance of the organic insulating materials can be improved for use in organic thin film transistors by utilizing an insulating polymer having a maleic imide copolymer structure. Despite some improvement, however, the copolymer structure is still soluble in organic solvents and will, as a result, tend to suffer some degree of degradation as a result of exposure to such solvents during subsequent photolithographic processing.
Other attempts have been made to improve the chemical resistance of the organic insulating film(s) during subsequent processing with organic solvents by mixing polyvinylphenol (PVP) with polymelamine-co-formaldehyde. These materials, however, are not generally suitable for use with plastic substrates because thermal processing necessary to achieve the desired cross-linking of the PVP requires heating to temperatures on the order of 200° C., temperatures that will tend to degrade or compromise certain desirable substrates.
In particular, patterning of organic insulating films for insulating adjacent electrodes and/or defining various regions is typically required during the fabrication of organic thin film transistors that may be used in, for example, display devices. One patterning method includes forming an organic insulating film by spin coating a polyimide layer, coating the polyimide with a photoresist layer, baking and exposing the photoresist layer using a conventional UV photolithographic process, developing the exposed photoresist layer, and etching the polyimide using the photoresist pattern as an etch mask as illustrated, for example, in FIG. 1. The organic insulating film may also be subjected to one or more surface treatments.
However, because this method employs a photolithographic process, the underlying organic insulating film must exhibit both superior thermal, developer and etch resistance relative to the overlying photoresist pattern in order to avoid being degraded during being degraded by the heating, developing and etching processes associated with photolithographic pattern formation. In addition, the organic insulating film should exhibit sufficient chemical resistance to endure the photoresist stripping process(es) used to remove the overlying photoresist after the etch has been completed.